Influence of carrier transport on drain-current variability of MOSFETs

We have investigated static variability of p-MOSFETs by evaluating the drain current under various conditions of gate and drain voltages. The value of drain current variability (σ_Id/Id) is proportional to (LW)^-1/2 before the short channel effect appears, being similar to that of Vt variability. The magnitude of σ_Id/Id decreases as the gate overdrive (Vg-Vt) decreases and classified into two regimes that corresponds to the carrier conduction mechanisms, i.e., diffusion and drift transports. This result strongly suggests that the dominant factors for determining σ_Id/Id values are related to the carrier conduction mechanisms.